Yup, you're screwed.
I was just there last weekend... My advice is to try to bribe someone at HKBAC. If they won't repo you to the airport outback (under your own power), you have to fly to Macau, which can be a 45 minute trip under the right conditions... (Think BOS to TEB). Mainland is a bad idea, Macau a little better.
If I got to choose, I'd rather fly an hour and be in Da Nang or Hanoi, seriously.
I think that the duty day argument may buy you a day, but I'm not sure.
FR